1. Field of the Invention
The present invention relates to rapid-set injection systems for improving soft ground, which is used in civil engineering works, and more particularly, to a rapid-set injection system using high-speed jet fluid, in which air, a cement hardening agent and a quick setting agent, respectively introduced along injection paths defined in an injection rod of the injection system inserted in a bore of the ground, are vigorously injected under high pressure to the soft ground, thus improving the soft ground.
2. Description of the Prior Art
In general, a method of improving soft ground is extensively known in the art, in which a monitor inserted in a bore of the ground is rotated and retracted upward while injecting a liquid-phase hardening agent, such as cement milk, thereby providing a pile-shaped solid body in the ground.
The conventional apparatuses using the above-mentioned method of improving the soft ground include a plurality of nozzles which are provided on an injection rod inserted in a bore of the ground. Thus, the liquid-phase hardening agent is injected under high pressure from the nozzles to the soil of the ground having the bore while the injection rod is rotated and retracted upward in the bore, thus improving the ground.
However, in the conventional apparatuses for improving the soft ground, the liquid-phase hardening agent is horizontally injected from the nozzles of the injection rod to the soil of the ground having the bore. Thus, the conventional apparatuses for improving the soft ground do not have desired permeability to evenly crush the soil of the ground, so that the infiltrating region of the hardening agent injected from the apparatuses is not even. Therefore, the conventional apparatus for improving the soft ground is problematic in that the size of the improved region of the ground is reduced, and the properties of the solid bodies formed in the improved ground are uneven.
To solve the above-mentioned problems, an apparatus with inclined nozzles for improving soft ground was proposed. However, in the conventional apparatus with the inclined nozzles, the inclined nozzles are arranged along the injection rod of the apparatus at large intervals. Furthermore, the inclined nozzles, arranged on the injection rod, inject the liquid-phase hardening agent to the ground in regular directions. Therefore, when the ground improvement work is executed in a deep bore of the ground, jamming of the injection rod in the deep bore of the ground may be undesirably caused. Furthermore, the conventional apparatus with the inclined nozzles is problematic in that slime, generated while the apparatus improves the ground, is not easily removed from the bore of the ground, thus disturbing formation of the desired solid bodies in the target ground.
Furthermore, a bit, provided on a lower end of the injection rod, vertically injects downward a fluid to the ground. Therefore, the injection rod may not provide a desired excavating force, so that the injection rod may not linearly move in the bore of the ground.
In addition, because a gel time during a ground improvement work using the apparatus with the inclined nozzles is indicated after the liquid-phase hardening agent is injected to the ground, it is very difficult to form desired solid bodies in the ground under water. Therefore, the conventional apparatus with the inclined nozzles cannot be used in a variety of ground improvement works.